(a) Technical Field
The present invention relates to a method for molding a highly heat-resistant sound absorbing and insulating material, which uses a sound absorbing material containing 20-80 parts by weight of a fiber material having a limiting oxygen index (LOI) of 25% or greater and a heat resistance temperature of 200° C. or greater and 20-80 parts by weight of a thermosetting binder resin having a heat resistance temperature of 200° C. or greater and is installed on an engine cylinder block and an automotive body panel above a muffler of a vehicle. More specifically, the method includes a releasing agent coating step of coating a releasing agent inside a hot die, a hot compression molding step of fixing a shape, and a cold compression step of stabilizing the shape.
(b) Background Art
Various noises are generated while driving a vehicle. The vehicle noise is mainly generated from an engine or an exhaust system and is transferred to the inside of a vehicle by air. A sound absorbing and insulating material is used to reduce the noise generated from the engine and the exhaust system from being transferred to the inside of the vehicle. An insulation dash, a dash isolation pad and the like are used to block the noise radiating from the engine from being transferred to the inside of the vehicle, and a tunnel pad, a floor carpet and the like are used to block the noise generated from the exhaust system and the floor from being transferred to the inside of the vehicle.
As sound absorbing materials for a vehicle, Korean Patent Publication No. 2004-0013840 discloses a 20-mm thick sound absorbing and insulating material having a PET fiber layer in which a synthetic resin film layer having a thickness of 40-100 μm in the lengthwise direction is inserted, and Korean Patent Publication No. 2002-0089277 discloses a process for preparing a sound absorbing insulation material of a nonwoven fabric form by cutting and beating a polyester fiber and an acrylic fiber, mixing with a low-melting-point polyester fiber at a specific ratio, and molding and heating the same. And, Korean Patent Publication No. 2006-0043576 discloses a method of coating at least one of a top layer and a bottom layer of a polyester (PET) felt with a resin, using a mixture fiber of a low-melting-point fiber (LMF) and a regular fiber.
However, for the existing insulation dash and insulation hood, although a resin felt using phenol powder as a binder, or a glass wool or semicrystalline polyurethane foam product using a phenol resin as a binder can be molded simply by a hot compression molding process within 60 seconds, they cannot maintain their shape under a high-temperature environment of 200° C. or greater or do not have superior flame retardancy. For this reason, they cannot be directly installed on an engine cylinder block or an automotive body panel above a muffler.
Further, a dash isolation pad, a tunnel pad and a floor carpet using a low-melting-point polyethylene terephthalate (LM-PET) fiber, which is a thermoplastic binder, have poor flame retardancy. Although a thermosetting binder resin having a heat resistance temperature of 200° C. or greater has to be used for direct installation on an engine cylinder block or an automotive body panel above a muffler, product molding is impossible through pre-heating followed by cold compression molding.